This invention relates, in general, to semiconductor devices, including, but not limited to, a semiconductor device having a large sense voltage.
Current mirror techniques have been used for current and voltage sensing in power MOSFETs. A conventional current mirror device provides an ability to perform substantially lossless current sensing in power control circuits. These devices are used in power supplies and motor controls. Current mirror devices have a small number of sense cells to sense voltage and current and a large number of power cells to switch and control electrical power to desired loads.
Although substantially lossless current sensing is an extremely desirable feature, the marketability of current mirror devices has been limited because of the relatively small amount of sense voltage that they produce. The sense voltage is small because the open mirror voltage (the sense voltage when the load on the sense cells is infinite) senses the voltage drop across the MOSFET channel only, which is only a small percentage of the voltage from drain to source (V.sub.DS(on)). In higher voltage devices, those having a breakdown voltage from drain to source (BV.sub.DSS) approximately greater than 200 volts, the usable amount of sense voltage is only about 10% of V.sub.DS(on). It would be desirable to increase the usable amount of sense voltage to a higher range for applications in which overcurrent shutdown must be initiated in order to be able to read the sense voltage above the noise.
In general, it would also be desirable to improve the integrity of the high voltage capability of semiconductor devices that utilize current mirror techniques. In addition, for some applications it would be desirable to improve the accuracy of the sensing capabilities.